Salinity in soil or water is one of the major stresses that affect crop production around the world. In Bangladesh the coastal areas are increasing day by day due to climate change. Therefore it is very important to investigate the mechanisms of salt tolerance. That is why, this study was undertaken to investigate the effect of salinity on tomato (Lycopersicon esculentum Mill.) by using ten genetically diverged tomato genotypes during seed germination and seedling growth stage. The study was carried out in Completely Randomized Design (CRD) with three replications under invitro condition. In the study, emergence percentage, radicle length, plumule length, Proline content, K+/Na+ of the seedling were assayed on five levels salinity; control (0), 4,8,12 and 16 dS m-1. The growth and subsequent development of tomato seedling negatively affected with the rising of salinity. Emergence percentage, radicle length, plumule length were decreased from control when salt concentration increased. Na+ content increased but K+ content decreased with the increment of salinity. The mean values of Na+/K+ ratio, varied from 4.2367 in control treatment to 0.00 at higher salinity level. Proline content was also increased with the increment of salinity which ranges from 9.55 to 41.5373 mg prol/2ml/sample at control to 16 dSm-1.The overall results of the experiment exhibited that among the genotypes BARI Tomato 2, Mintoo and Unnoyon were comparatively more tolerant to higher salinity on the basis of studied parameters.